Vanos Rebuild Start Hesitation

[sapote]

I will do eventually, though from what I understand the car doesn't use these initially and is open loop until they warm up, so it wouldn't be the cause of the start hesitation.

I'd really like to get to the bottom of the start issue first, and then I have brakes to sort 😑

Yes and no. There is enough data from the log to show pre cat sensor1 is slow to react, and also during the SAP running period, the extra oxygen should cause the precat sensor signals to be below 0.1v, but they are not. These are the symptom of old and slow sensors.
If the pre cat sensors are bad and can mess up the fuel trim -- and let's assume they caused the rich fuel trim with -7 LTFT before engine shut off, then when engine started again, DME will use the last LTFT of -7 during cranking, and it might affect how the engine starts.

I don't know what will impact the hard starting, but I would try to fix the high negative fuel trim and fuel status 8 first.

[jamesfoley]

Yes and no. There is enough data from the log to show pre cat sensor1 is slow to react, and also during the SAP running period, the extra oxygen should cause the precat sensor signals to be below 0.1v, but they are not. These are the symptom of old and slow sensors.
If the pre cat sensors are bad and can mess up the fuel trim -- and let's assume they caused the rich fuel trim with -7 LTFT before engine shut off, then when engine started again, DME will use the last LTFT of -7 during cranking, and it might affect how the engine starts.

I don't know what will impact the hard starting, but I would try to fix the high negative fuel trim and fuel status 8 first.

Might explain the random lean code I got not too long ago, but still weird that none of the codes or behaviour is consistent. Would have thought if the LTFTs were enough for it to be too lean at crank it would happen all the time 🤔 I thought +/- 5 was considered okay?

On that logic then the car should start without any hesitation if the fuel adaptations are reset right? Though I think resetting those also reset ignition and vanos adaptations as well which might make things unhappy, so might not be a good test

[sapote]

I'm not totally blaming the LTFT for the hard start, but it is and the fuel status 8 are the good target to shoot them down, then hopefully the hard start might go away.

[jamesfoley]

Sorry to bring this thread up again, but just wanted to ask if anyone knows if a drop in either exhaust or intake camshaft position signals would result in a fuel system state change?

Also wanted to ask if there was a way to monitor the intake cam position sensor without using an oscilloscope? Unless graphing the VANOS intake position like I was before in TestO is the way?

[sapote]

Sorry to bring this thread up again, but just wanted to ask if anyone knows if a drop in either exhaust or intake camshaft position signals would result in a fuel system state change?

Also wanted to ask if there was a way to monitor the intake cam position sensor without using an oscilloscope? Unless graphing the VANOS intake position like I was before in TestO is the way?

Checking the sensor is easy with a DVM, but monitoring with engine running must be done with a scope. Are you thinking the sensor is intermittently bad? I don't believe it because the fuel status is good at idle, and went bad during driving -- so why the sensor gone bad during driving and not idle, consistently as shown in the log files?

[jamesfoley]

Checking the sensor is easy with a DVM, but monitoring with engine running must be done with a scope. Are you thinking the sensor is intermittently bad? I don't believe it because the fuel status is good at idle, and went bad during driving -- so why the sensor gone bad during driving and not idle, consistently as shown in the log files?

• Long crank
• Hard rough start
• Instantly stalling after starting
• Almost stalling when coming to a stop

All the above make me believe that I have a soft failing intake camshaft sensor, or perhaps someone has fitted an eBay sensor before my ownership. Almost as if the sensor is too weak to read the trigger wheel sometimes.

The shop that did the VANOS and fuel pressure regulator did say it sounds like a fuel delivery issue, but more along the lines of a blocked line. I figured if I had a blocked fuel line I’d have starting issues all the time, and misfires especially at WOT.

[jamesfoley]

Another not so interesting update. I cleaned the ICV today just to see if I’d get lucky there, but from what I can tell it hasn’t made any difference. It was definitely very dirty, and not as free moving compared to after I cleaned it. Throttle response from idle is a litre snappier now if anything, and it bogs down less when pulling away. Unsure if adaptations need clearing?

At least it was an easy exercise to understand how much of a pain in the arse the plenum hose clamps are. I know they’re not technically reusable, but got away with reusing 3. The others were fused together and I had to break them to free them. Some generic jubilee clips work for now, I just made sure they didn’t interfere with the throttle. Will most likely replace these when the plenum comes off again…

[sapote]

Did you replace the pre cat O2 sensors?

[jamesfoley]

Did you replace the pre cat O2 sensors?

Bit of a late reply, but just sorting things as soon as my wallet allows. Both pre-cat O2 sensors have been replaced now and produced this log: https://datazap.me/u/jamesfoley/e46-.../?log=0&data=1

I'm going to assume that because I still have fuel system faults I potentially have issues with fuel delivery, something between the injectors and the fuel pump?

Can also confirm it did nothing for my hard start issue.

[sapote]

Just adding these two datalogs

Drive from cold: https://datazap.me/u/jamesfoley/e46-...ta=2-3-4-10-12
Drive from warm: https://datazap.me/u/jamesfoley/e46-...ta=2-3-4-10-12

Both times the car started without hesitation, but the logs still have a lot of fuel status 8's. Only pattern I can see is the post cat O2 sensors dip mostly where the status 8's appear.

39C or 102F is not a cold engine. When cold I meant in the cold morning so we can see if the SAP pump is working and how the O2 sensors acting at old condition.

[sapote]

Bit of a late reply, but just sorting things as soon as my wallet allows. Both pre-cat O2 sensors have been replaced now and produced this log: https://datazap.me/u/jamesfoley/e46-.../?log=0&data=1

I'm going to assume that because I still have fuel system faults I potentially have issues with fuel delivery, something between the injectors and the fuel pump?

Can also confirm it did nothing for my hard start issue.

This log doesn't have enough data. Try it again with the same data as in post #77, but get one starting at cold morning in the 60s or lower. Then a warm with idling and driving.
However, the MAF looks good with around 4g/s at idle.

[jamesfoley]

This log doesn't have enough data. Try it again with the same data as in post #77, but get one starting at cold morning in the 60s or lower. Then a warm with idling and driving.
However, the MAF looks good.

I pulled PIDs to get higher resolution O2 sensor data, with all the PIDs the data rate is a bit slow. I'll get a couple more logs tomorrow though with all the PIDs back in. Currently using an OBDLink MX+ and the OBDLink app on my iPhone (which is basically OBD Fusion), not sure if there is a faster way to poll data.

Only things I've yet to replace now are the camshaft sensors, throttle position sensors, and injectors.

[jamesfoley]

sapote Here is a cold and warm start log.

Cold: https://datazap.me/u/jamesfoley/e46-...d?log=0&data=2
Warm: https://datazap.me/u/jamesfoley/e46-...m?log=0&data=2

I cleared the adaptations before starting the cold log as you can see the long term fuel trims start at 0, but they do end up back in the negatives by the end of the warm log. Worth noting that none of the above starts where "hard", started on the key as expected.

Forgot to mention, A/C was on here which might explain the higher MAF rate.

[sapote]

I pulled PIDs to get higher resolution O2 sensor data, with all the PIDs the data rate is a bit slow. I'll get a couple more logs tomorrow though with all the PIDs back in. Currently using an OBDLink MX+ and the OBDLink app on my iPhone (which is basically OBD Fusion), not sure if there is a faster way to poll data.

Only things I've yet to replace now are the camshaft sensors, throttle position sensors, and injectors.

Needed PIDs: coolant temp, all 4 O2 sensors, MAF, fuel status1, fuel trims, rpm,
No need: time, car speed, ignition timing, power supply voltage, load, fuel status2 (exact image of status1) , intake air temp (we already know it's good)

[sapote]

sapote Here is a cold and warm start log.

Cold: https://datazap.me/u/jamesfoley/e46-...d?log=0&data=2
Warm: https://datazap.me/u/jamesfoley/e46-...m?log=0&data=2

I cleared the adaptations before starting the cold log as you can see the long term fuel trims start at 0, but they do end up back in the negatives by the end of the warm log. Worth noting that none of the above starts where "hard", started on the key as expected.

Forgot to mention, A/C was on here which might explain the higher MAF rate.

Please don't turn on the AC for the test. Do hot idle again to confirm MAF is around 4g/s at idle and not 6.
The cold log proves that the precat sensors are working perfect -- deep low during extra air from the SAP running, and switching normally after that.
I was hoping the cause of fuel status 8 was due to bad MAF of 6g/s at idle, until seeing that the AC was on.

If MAF is indeed around 4 at idle, then it will be a challenge to find out the cause of status 8 but blaming the leaking injectors.
What is the injectors history?